Generally, an electrical box includes internal securing means for securing an electrical accessory, and includes external fastener means for fastening to a wall.
An ordinary electrical box further includes, in its rear portion, knock-out diaphragms that make it possible to open the rear wall of the box locally so as to insert, into its inside volume, routing conduits from which there emerge the electrical conductors necessary for serving the electrical accessory.
Electrical boxes present sizes that are standard. Thus, currently, a circular electrical box for flush mounting presents a standard diameter of 68 millimeters (mm) and usually a depth of 40 mm.
The inside volume of such an electrical box is thus small and it is awkward to house therein not only the electrical accessory, but also the end of the routing conduit and the ends of the electrical conductors that have been pulled into the inside volume of the electrical box, in particular because of the stiffness of the electrical conductors that need to be bent between the electrical accessory and the rear wall of the box.
In addition, the small inside volume restricts any possible development of electrical accessories that are prevented from incorporating all of the functions that might be desired, because of their limited size.
A solution currently used for housing voluminous electrical accessories thus consists in providing two electrical boxes side by side, with one housing the electrical accessory, while the other houses the electrical conductors.
However, that solution turns out to be costly and tricky to implement.
Another solution is described in document EP 2 068 411. That other solution consists in using an electrical box that has a slot formed in its rear wall through which it receives a connector that is adapted to make it easier to connect the electrical accessory to the electrical conductors that protrude from the routing conduit. For this purpose, the connector includes electrical terminals that are accessible from the inside of the box for connecting the electrical accessory, and a cable portion for connecting to the electrical conductors.
That solution avoids having to insert the electrical conductors and the routing conduits into the inside volume of the electrical box, thereby making it possible to make more space available for the electrical accessory.
The major drawback of that solution is that it does not make it possible to block the end of a routing conduit against the box. That solution thus requires either the entire electrical installation to be made with electric cables of the type having insulated electric wires embedded in a common insulating sheath (which turns out to be more expensive than using routing conduits through which insulated electric wires can be drawn freely), or else expensive means to be provided for creating a connection piece between the electric cable and a routing conduit.
In addition, document U.S. Pat. No. 3,879,101 discloses an electrical accessory for engaging in a flush-mounted box in the rear wall of which a cable inlet opening is provided. The electrical accessory is made of two portions, having a functional portion at the front and a connection portion at the rear.
In that document, the rear connection portion makes it easier to change the front connection portion, but it does not make it possible to increase the volume available inside the box for fitting voluminous mechanisms therein. Specifically, it is still necessary to provide space inside the box for connecting the electric wires to the connection portion.